A high-modulus low-shrinkage polyester industrial yarn and its preparation method

ABSTRACT

A high-modulus low-shrinkage polyester industrial yarn obtained by subjecting a polyester to dissolution, washing and solid state polycondensation followed by spinning. The high-modulus low-shrinkage polyester industrial yarn has a dry heat shrinkage rate of 2.0±0.25% under test conditions of 177° C.×10 min×0.05 cN/dtex. The average value of the crystal volume VC of the high-modulus low-shrinkage polyester industrial yarn is larger than 230 mm3. The high-modulus low-shrinkage polyester industrial yarn has a fiber modulus of ≥100 cN/dtex. The polycondensation catalyst consists of magnesium ethylene glycol and antimony ethylene glycol, which has a small thermal degradation coefficient.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the national stage entry of InternationalApplication No. PCT/CN2016/085410, filed on Jun. 12, 2016, which claimsthe benefit of priority from Chinese Patent Application No.CN201511017953.X, filed on Dec. 29, 2015, the entire contents of whichare incorporated herein by reference.

TECHNICAL FIELD

The present invention belongs to the technical field of the preparationmethod of the polyester industrial yarn. The present invention relatesto a high-modulus low-shrinkage polyester industrial yarn and itspreparation method. To be specific, the polyester and the high-moduluslow-shrinkage polyester industrial yarn using the mixture of magnesiumethylene glycol and antimony ethylene glycol as the condensationcatalyst, and scouring and washing the polyester sections with water andrinsing agent at 120-130° C., and 0.2-0.3 MPa.

BACKGROUND

Polyethylene terephthalate (PET) is a kind of polymer with excellentperformance. PET is preferred because of its high modulus, highstrength, crispness, good shape retention, safe and clean, and goodbarrier property. It is widely used in fiber industry, bottle packaging,film production and sheets materials, etc. The output production of PETis increasing year by year and its status in the industry has beensignificantly improved.

Industrial polyester fiber mainly refers to those used in industry,national defense, medical care, environmental protection andcutting-edge science. It is a kind of chemical fiber which hasrelatively special physical and chemical structure, properties and uses,or with special functions. The characteristics can be found in itsresistance against strong corrosion, wearing, high temperature,radiation, fire, burning, high voltage current. It also has highstrength and high modulus, and a variety of medical usage. The tentcloth using the high strength and low shrinkage polyester industrialfilament has high peel strength and tear strength, which make the tentcloth suitable for various purposes, including flexible advertisinglight box materials, inflatable structural materials, tent-likebuildings' fabric sunshade tent and so on. The high strength and lowshrinkage industrial yarn-based fabric materials are also applied inspecial protective clothing, camouflage, covering, backpack and othermilitary supplements. As a kind of geotextile material with theadvantages of light, soft, high strength, wear-resistant,corrosion-resistant, non-conductive, shock absorption and so on, it isalso reliable and convenient to use. It can make our work moreefficient, and will not damage the lifting objects. The expansion ofindustrial polyester fiber's applications has led the whole fiberindustry to a more competitive edge in application areas. Polyesterhigh-performance fibers are playing an increasingly important role inmany aspects including reducing the weight of composite materials,durability in use and reducing maintenance costs and so on. In the nextfew decades, the development of high-performance polyester fiber is notonly the progress of its amount, but also the development in the fieldof application and enhancement of the overall competitiveness of theindustry chain to achieve substantial results.

High strength, high modulus, low shrinkage, dimensional stability,functionalization will be the main direction of the development ofindustrial polyester fiber. The fiber quality is related to thecollection of polyester polymer structure, mainly related to theintermolecular force, crystal morphology and structure, orientationstate structure, etc., and the shape and structure of the crystal is oneof the key points. Polyester industrial yarn is widely used in differentfields. The high-modulus low-shrinkage polyester industrial yarnaccording to the present invention has the characteristics of lower dryheat shrinkage and better dimensional stability.

Carboxyl end group, oligomer, and diethylene glycol (DEG) content areimportant quality indicators of polyester sections, in which oligomerand diethylene glycol are low molecular polymer. These reflect not onlythe quality of production status, but also affect the product qualityafter the spinning process. Therefore, reducing the carboxyl end groups,oligomers diethylene glycol content in polyester sections play animportant role in improving the quality of polyester products. Theinfluence of carboxyl end groups on the performance of polymers cannotbe ignored. Only by controlling the amount of polyester end carboxylgroups in the production, can we stabilize the uniformity of molecularweight distribution. The amount of diethylene glycol in the polyestersections is a very important quality index in polyester production.Because it has a direct impact on the melting point of polyestersections, the melting point of polyester sections will decline sharplywith the increase of DEG content, so it not only reflects the quality ofproduction, but also directly affects the post-processing and spinningprocess and silk quality. Oligomer in polyester is low molecular polymerwith degree of polymerization of less than 10 and can be classified intolinear oligomers and cyclic oligomers, of which the majority are cyclicpolymers, especially cyclic trimers. The oligomer is mainly influencingheterogeneous nucleation spinning processing, the performance ofpolyester and after processing caused some adverse effects. Controllingthe content of the three in polyester sections is a very important issuein the polyester production process.

SUMMARY

The present invention is to provide a high-modulus low-shrinkagepolyester industrial yarn and its preparation method. To be specific,the present invention discloses the preparation method of a high-moduluslow-shrinkage polyester industrial yarn and the polyester prepared byusing a mixture of magnesium ethylene glycol and antimony ethyleneglycol as polycondensation catalyst. The high-modulus low-shrinkagepolyester industrial yarn in the present invention has a dry heatshrinkage of 2.0±0.25% at 177° C.×10 min×0.05 cN/dtex. The average valueof the crystal volume Vc of the high-modulus low-shrinkage polyesterindustrial yarn according to the present invention is larger than 230nm³. The high-modulus low-shrinkage polyester industrial yarn accordingto the present invention has a fiber modulus of ≥100 cN/dtex. In thepresent invention, a mixture of magnesium ethylene glycol and antimonyethylene glycol is used as a polycondensation catalyst to reduce thermaldegradation to minimum, and the polyester sections are scoured andwashed at 130° C. and 0.3 MPa with water and a rinsing agent, in orderto lower the influence of carboxyl end group, oligomer and diethyleneglycol content on polyester spinning process.

Additionally, a high-modulus low-shrinkage polyester industrial yarnaccording to the present invention is obtained by the esterification ofterephthalic acid and ethylene glycol and the polycondensation catalyzedby a mixture of magnesium ethylene glycol and antimony ethylene glycol,polyester section is obtained by granulating. Then the polyester sectionis ready for dissolution, washing and solid state tackifying andspinning.

A process for preparing the high-modulus low-shrinkage industrial yarn,wherein the carboxyl end group is less than 15 mol/t, the masspercentage of oligomer is lower than 0.5%, and weight percentage ofdiethylene glycol is lower than 0.5%.

A process for preparing the high-modulus low-shrinkage industrial yarn,wherein the molecular formula of magnesium ethylene glycol isMg(OCH₂CH₂OH)₂.

A process for preparing the high-modulus low-shrinkage industrial yarn,wherein the dissolution and washing refers to that the granulatedsections are scoured and washed with water and a rinsing agent at120-130° C. and 0.2-0.3 MPa.

High strength, high modulus, low shrinkage, dimensional stability,functionalization will be the main direction of the development ofindustrial polyester fiber, and what affects the fiber quality is theaggregate structure of polyester polymer, which is mainly related to theintermolecular force, crystal morphology and structure, orientationstate structure, etc. Among them, the shape and structure of the crystalis one of the key points.

Low shrinkage and dimensional stability are the main factors that makehigh quality polyester. The macroscopic heat shrinkage of polyesterfibers is due to the entropy change tendency of the macromolecularchains of local elongation, including the internal stress caused by thedevelopment of the crimp state and the axial internal stress frozen inthe spinning process in the sample, this local internal stress can betransmitted from the molecular network structure to the entire material,which will occur when the outside world to provide enough heat.

Polyester fibers are oriented semi-crystalline polymer materials, whichare composed of structural units with different orientation stability:(1) high-stability and high-perfection crystalline parts; (2) relativelylow-stability imperfect crystalline parts: (3) low-stability transitionlayer between crystalline and amorphous; (4) Unstable oriented amorphousphase. When the polyester fiber is heated, things may happen asfollowed, the oriented amorphous phase is retarded and crystallized;failure of the imperfect crystalline portion and recrystallization mayoccur: thickening of the crystal grains or complete melting of thecrystal grains. It shows that the grain size and the degree of crystalrefinement are the important factors to affect the dimensional stabilityof the fiber at high temperature. The low thermal shrinkage at 177° C.is an excellent thermal dimensional stability fiber with two structuralfeatures: large grain size and good crystallinity. Therefore, the fibergrain size and crystallization of good integrity, is the guarantee oflow shrinkage fiber's quality.

The main factors affecting the crystallization of polyester are: 1. thestructure of the molecular chain itself. 2. the choice ofcrystallization temperature. 3. the impact of molecular weight. 4. theapplication of nucleating agent. 5. Finally, the impact of preparationmethod. Nucleation is a very important part of crystallization, and thenucleating agent to some extent can speed up the crystallizationprocess, while the more important thing to polyester industrial yarn isthe impact of the size and perfection of the crystallization.

If the content of carboxyl end group is high in polyester, the thermalstability of polyester resin is poor; while the carboxylate salt of bigpolyester molecular chain is formed by the reaction of the carboxylateand polyester, which constitutes a nucleus that can accelerateheterogeneous nucleation of the polyester. Polyester contains 3-4% ofoligomers, mostly in the form of low molecular ether and ester, mainlycyclic oligomer, and diethylene glycol. The influence of oligomers thequality of the polyester cannot be ignored. They can affect thecrystallization nucleation mechanism, crystallinity, crystal morphologyand crystallization integrity of the polyester mainly in the form ofnucleating agent, thereby affecting the quality of the polyester fiber,especially the thermal shrinkage of the polyester industrial yarn. Purepolyester without diethylene glycol will not exhibit abnormalspherulitic morphology regardless of the crystallization conditions;however, when the sample contains diethylene glycol, normal and abnormalspherulites will coexist in the crystalline zone, and as the content ofdiethylene glycol increases, the proportion of abnormal spherulitesincreases in the entire morphology, thereby affecting the integrity ofthe crystals and reducing the crystallinity of the polyester. Cyclictrimer in the polyester to nucleate more ways, more nucleating agent,crystallization speed, the number of large grains, but the smaller grainsize, and thus affect the integrity of the crystallization.Heterogeneous nucleation increased, making high degree of stability andhigh degree of completion of the part of the crystal to reduce, and theenlargement of transition layer between imperfect crystalline portionwith relatively low stability and low-stability crystalline andamorphous increases the polyester fiber shrinkage has an adverse effecton the thermal shrinkage of the polyester fiber.

The high-modulus low-shrinkage polyester industrial yarn according tothe present invention, characterized in that the density deviation ofsaid high-modulus low-shrinkage industrial yarn≤1.5%, breakingstrength≥7.0 cN/dtex, CV value of breaking strength≤2.5%, breakingextension 12.0±1.5%, CV value of breaking extension≤7.0%.

In the process for preparing the high-modulus low-shrinkage polyesterindustrial yarn, the mixture of magnesium ethylene glycol and antimonyethylene glycol, the mass ratio of the two is 2:1 to 3:1.

A process for preparing the high-modulus low-shrinkage polyesterindustrial yarn according to the present invention, characterized inthat the polyester is obtained by the esterification of terephthalicacid and ethylene glycol and the polycondensation catalyzed by a mixtureof magnesium ethylene glycol and antimony ethylene glycol, polyestersection is obtained by granulating. Then the polyester section is readyfor dissolution, washing and solid state polycondensation. Finally,after measuring, extrusion, cooling, oiling, stretching, heat settingand winding, the high-modulus low-shrinkage polyester industrial yarn isprepared.

A process for preparing the yarn according to the present invention,characterized in that the preparation method of the high-moduluslow-shrinkage polyester industrial yarn includes:

a. The Preparation of Catalyst (Magnesium Ethylene Glycol)

Add ethylene glycol in the single-compartment electrolytic cellmagnesium chloride is the supporting electrolyte, the anode is comprisedof magnesium, the cathode is graphite. At 50 to 60° C., the apparatus isoperated about 10 to 12 h under DC, for the initial voltage 6 to 10V,cathodic current density 150 to 200 mA. After the electrolysis, thewhite suspension liquid is obtained followed by removing the electrodes,decompression filtration and washing by anhydrous alcohol, then weobtain the magnesium ethylene glycol after drying.

b. The Preparation of Polyester, Including the Esterification andPolycondensation

The esterification reaction uses terephthalic acid and ethylene glycolas raw materials, adding polyether-inhibitor in to obtain esterificationproducts after reaction. The esterification reaction needs the increaseof pressure in the nitrogen atmosphere, and the pressure is controlledin the scale of atmospheric pressure to 0.3 MPa, the temperature iscontrolled between 250 to 260° C. The end of the reaction is set afterthe amount of distillate water in the esterification reaction reaches90% of the theoretical value at least. The condensation reaction,includes the low vacuum stage and the high vacuum stage of thecondensation reaction:

In the low vacuum stage of such condensation reaction, the catalyst andstabilizer need to be added into the esterification production. Thecondensation reaction will start under the condition of negativepressure. In such period, the pressure needs to be pumped smoothly fromatmospheric pressure to the pressure lower than the absolute pressure500 Pa, and the temperature needs to be controlled between 260 to 270°C. The reaction time should be 30 to 50 mins. The catalyst the reactionused is the mixture of magnesium ethylene glycol and antimony ethyleneglycol.

The high vacuum stage of the condensation reaction requires continuouslypumping vacuum after the low vacuum period in order to ensure that thereaction pressure is decreased to absolute pressure lower than 100 Pa.The reaction temperature needs to be controlled between 275 to 280° C.,and the reaction time needs to be 50-90 mins.

Then the polyester is prepared and the polyester section can be madethrough granulation.

c. Dissolution and Washing

The polyester section is scoured and washed with water and rinsing agentat 120 to 130° C. and 0.2 to 0.3 MPa for 3 to 5 h followed by washingwith water.

d. Solid State Polycondensation

The intrinsic viscosity of the polyester section is raised to 1.0 to 1.2dL/g through the solid state polycondensation, it can be regarded ashigh-viscosity chips.

e. Main Process Parameters of Spinning

The temperature of extrusion is 290 to 310° C.;

The air temperature of cooling is 20 to 30° C.;

The process of stretching and heat setting,

GR-1 at speed of 3000 to 3600 m/min, temp: 75 to 80° C.;

GR-2 at speed of 3800 to 4500 m/min, temp: 85 to 95° C.;

GR-3 at speed of 5000 to 5600 m/min, temp: 250 to 255° C.;

GR-4 at speed of 5500 to 5600 m/min, temp: 250 to 255° C.;

GR-5 at speed of 5630 to 5650 m/min, temp: 250 to 255° C.;

GR-6 at speed of 5500 to 5600 m/min temp: 250˜255° C.;

The winding speed is 5450 to 5500 m/min.

A process for preparing the yarn according to the present invention,characterized in that the molar ratio of the ethylene glycol toterephthalic acid is 1.2:1 to 2.0:1.

A process for preparing the yarn according to the present invention,characterized in that the mass ratio of magnesium ethylene glycol toantimony ethylene glycol in their mixture is 2 to 3:1. The mass of thecatalyst is 0.01-0.05% of the terephthalic acid.

The use of magnesium glycol and antimony ethylene glycol mixture as apolycondensation catalyst is because that magnesium glycol is relativelymild, the thermal degradation coefficient is small, less side reactionscaused during the reaction, which can reduce terminal carboxyl andoligomer in production. The main factors causing thermal degradation arehigh temperature and the catalyst. High temperature is because thereaction strength is too high, leading to accelerated degradation, whichresults in carboxyl end groups, but also increases the cyclic oligomer.Catalyst is related to the catalyst degradation reaction constant. Inpolycondensation process, the role of the catalyst is not only tocatalyse the formation of the main reaction, and to affect the rate andyield of the reaction, but also to catalytic thermal degradation andether bond formation, increase the content of diethylene glycol, therebyincreasing the content of carboxyl end groups.

A process for preparing a high-modulus low-shrinkage polyesterindustrial yarn, wherein the stabilizer is chosen from triphenylphosphate, trimethyl phosphate and trimethyl phosphite. The mass ofstabilizer is 0.01 to 0.05% of the terephthalic acid. Stabilizers aremainly phosphate ester, whose function is to capture the reactiongenerated during the polymerization of free radicals, and reduce sideeffects.

A process for preparing high-modulus low-shrinkage polyester industrialyarn, wherein the mass ratio of the water and the rinse agent is 100:4to 100:3, the ratio of polyester sections and water and the rinse agent,that is, the solid-liquid ratio is 1:10 to 1:5. The rinsing agent ischosen from ethylene glycol monoethyl ether, ethylene glycol monopropylether and ethylene glycol monobutyl ether. Add a small amount of rinsingagent to the water, and rinsing agent dissolves in water, and it canalso dissolve most of the low molecular ether and ester, which helps toimprove the washing effect and oligomer reduction.

A process for preparing a high-modulus low-shrinkage polyesterindustrial yarn, wherein the washed polyester sections are washed withhot water at 70-80° C. for 10-15 mins after brewing, washed with coldwater, dried and cooled and reserved.

A process for preparing a high-modulus low-shrinkage polyesterindustrial yarn, the polyether inhibitor is chosen from sodium acetateand calcium acetate, the mass of polyether-inhibitor agent is 0.01-0.05%of terephthalic acid. The polyether-inhibitor agent reduces theformation of ether under acidic conditions by adding a small amount ofNaAc, thereby reducing the reaction of ethylene glycol to diethyleneglycol.

The present invention is intended to provide a high-moduluslow-shrinkage polyester industrial yarn which employs a relatively mildtype of polycondensation catalyst, magnesium ethylene glycol. With lessside reaction induced during the reaction and less thermal degradationduring processing, it reduced the production of oligomers in theprocess. Polyester sections were brewed at 130° C. and 0.3 MPa withwater and solvent, which improved the washing effect and oligomerreduction. The reduction of oligomer in polymerization process, and thereduction of the thermal degradation during processing, greatly reducethe impurities in the polyester, and also reduce the amount ofnucleating agent in the polyester, and increase homogeneous nucleationrate on the basis of the reduction of heterogeneous nucleation. It isconducive to high-modulus low-shrinkage polyester industrial fibers inthe grain size growth and crystallization optimization.

Benefits:

-   -   This method uses the mixture of magnesium glycol and antimony        ethylene glycol as a polycondensation catalyst. Magnesium glycol        is relatively mild, the thermal degradation coefficient is        small, and fewer side effects in the reaction process reduce        production of terminal carboxyl and oligomer in process.    -   The content of carboxyl groups in the polyester sections is less        than 15 mol/t, the content of oligomers is less than 0.5% and        the content of diethylene glycol is less than 0.5%, which is        beneficial to further improve the fiber quality.    -   Polyester sections can be washed with water and the detergent at        120˜130° C. and 0.2˜0.3 MPa improve the washing effect and        reduce the oligomer.    -   Polyether-inhibitor agent reduces the formation of ether under        acidic conditions by adding a small amount of NaAc, which        reduces the activity of ethylene glycol to diethylene glycol.    -   Oligomer's decreasing during polymerization, and the reduction        of thermal degradation during the process, greatly reduce the        impurities in the polyester, and also reduce the amount of        nucleating agent in polyester, and increase homogeneous        nucleation rate on the basis of reducing the heterogeneous        nucleation in the process, which is conducive to high-modulus        low-shrinkage polyester industrial fiber grain size growth and        crystallization of the optimization.

DETAILED DESCRIPTION

Hereinafter, the present invention will be described in more detail bythe following examples, but not limited thereto. It should be noticedthat these examples are only for illustrating the present invention andare not intended to limit the scope of the present invention. Inaddition, it should be noticed that after reading the content of thepresent invention, those skilled in this field can make variousmodifications or changes to the present invention, and these equivalentforms also apply to the scope of the appended claims of thisapplication.

A high-modulus low-shrinkage polyester industrial yarn, whereincharacterized in that the high-modulus low-shrinkage polyesterindustrial yarn according to the present invention is obtained bysubjecting a polyester to dissolution, washing and solid statepolycondensation followed by spinning. The high-modulus low-shrinkagepolyester industrial yarn according to the present invention has a dryheat shrinkage rate of 2.0±0.25% under test conditions of 177° C.×10min×0.05 cN/dtex. The average value of the crystal volume Vc of thehigh-modulus low-shrinkage polyester industrial yarn according to thepresent invention is larger than 230 mm³. The high-modulus low-shrinkagepolyester-industrial yarn according to the present invention has a fibermodulus of ≥100 cN/dtex. The polyester according to the presentinvention is obtained by the esterification of terephthalic acid andethylene glycol and the polycondensation catalysed by a mixture ofmagnesium ethylene glycol and antimony ethylene glycol followed bygranulation. The high-modulus low-shrinkage industrial yarn has thecarboxyl end group less than 15 mol/t, the mass percentage of oligomerlower than 0.5%, and weight percentage of diethylene glycol lower than0.5%. The molecular formula of magnesium ethylene glycol isMg(OCH₂CH₂OH)₂.

A process for preparing the high-modulus low-shrinkage industrial yarn,wherein the dissolution and washing refers to that the granulatedsections are scoured and washed with water and a rinsing agent at120-130° C. and 0.2-0.3 MPa.

The high-modulus low-shrinkage polyester industrial yarn has the densitydeviation of said high-modulus low-shrinkage industrial yarn≤1.5%,breaking strength≥7.0 cN/dtex, CV value of breaking strength≤2.5%,breaking extension 12.0±1.5%, CV value of breaking extension≤7.0%.

In the process for preparing the high-modulus low-shrinkage polyesterindustrial yarn, the mixture of magnesium ethylene glycol and antimonyethylene glycol, the mass ratio of the two is 2:1 to 3:1.

EXAMPLE 1

A process for preparing a high-modulus low-shrinkage polyesterindustrial yarn, wherein the main process is:

1. Preparation of Catalyst Magnesium Glycol:

Add ethylene glycol into the single-compartment electrolytic cell,magnesium chloride is electrolyte, the anode is magnesium, the cathodeis graphite. Under DC, the initial voltage is 6V, the cathode currentdensity is 150 mA, and electrolysis is carried out for 10 hours at 50°C. Remove the electrode after the electrolysis, we can get whitesuspension. Filter it under reduced pressure, wash the white solid withanhydrous ethanol, and we get magnesium ethylene glycol.

2. Preparation of Polyester, Including Esterification andPolycondensation:

Esterification Reaction:

Using terephthalic acid and ethylene glycol as raw materials, ethyleneglycol and terephthalic acid molar ratio of 1.2:1, addingpolyether-inhibitor sodium acetate, sodium acetate dosage ofterephthalic acid in an amount of 0.01% by weight. Start esterificationreaction under nitrogen atmosphere pressure, and control the pressure atatmospheric pressure, the temperature at 250° C. When esterified waterdistillate amount reaches 91% of the theoretical value of theesterification, reaction ends.

Polycondensation Reaction:

Including polycondensation reaction of low vacuum phase andpolycondensation reaction high vacuum phase:

In the polycondensation reaction low-vacuum stage, add catalyst and thestabilizer acid triphenyl ester into the esterification product. Theacid triphenyl ester dosage is 0.01% of terephthalic acid by weight, andthe amount of catalyst is 0.01% of terephthalic acid by mass. Thepolycondensation reaction is started under the condition of negativepressure, the pressure is steadily pumped from the atmospheric pressureto the absolute pressure of 498 Pa, the temperature is controlled at260° C., and the reaction time is 30 minutes. The catalyst is a mixtureof magnesium ethylene glycol and antimony ethylene glycol, in whichmagnesium glycol and antimony ethylene glycol mass ratio is 2:1;

After the polycondensation reaction in the low-vacuum stage, the vacuumis continued to reduce the reaction pressure to 98 Pa, the reactiontemperature is controlled at 275° C., and the reaction time is 50minutes. The polyester sections are obtained by granulation.

3. Solvent Cleaning

Polyester sections are washed with water and rinsing agent ethyleneglycol monoethyl ether at 120° C. and 0.2 MPa for 3 hours. Afterwashing, the polyester sections are washed with hot water at 70° C. for10 minutes and then washed with cold water. After drying and cooling,the mass ratio of water to the rinsing agent is 100:3, the ratio of thepolyester section to the water and the rinsing agent, that is, the solidto liquid ratio is 1:5;

4. Solid-Phase Polycondensation:

The obtained polyester sections are solidified by polycondensation toincrease the intrinsic viscosity of the polyester sections to 1.0 dL/g,that is, high-viscosity sections.

5. The Main Process Parameters in Spinning:

The temperature of extrusion is 290° C.,

The air temperature of cooling is 20° C.,

The process of stretching and heat setting:

GR-1 speed 3000 m/min, temp: 75° C.,

GR-2 speed 3800 m/min, temp: 85° C.,

GR-3 speed 5000 m/min, temp: 250° C.,

GR-4 speed 5500 m/min, temp: 250° C.,

GR-5 speed 5630 m/min, temp: 250° C.

GR-6 speed 5500 m/min, temp: 250° C.,

The winding speed is 5450 m/min.

The high-modulus low-shrinkage polyester industrial yarn obtained underthe conditions of a temperature of 177° C.×10 min×0.05 cN/dtex has thedry heat shrinkage rate of 2.25%. The high-modulus low-shrinkagepolyester industrial yarn according to the present invention has theaverage value of the crystal volume Vc of 232 nm³ and a fiber modulus of110 cN/dtex. Additionally, the linear density deviation rate is 1.5%,breaking strength is 7.1 cN/dtex, CV value of breaking strength is 2.6%,breaking extension is 12.5% and CV value of breaking extension is 7.0%.

EXAMPLE 2

A high-modulus low-shrinkage polyester industrial yarn preparationmethod, the main process is:

1. Preparation of Catalyst Magnesium Glycol:

Add ethylene glycol into the single-compartment electrolytic cell,magnesium chloride is electrolyte, the anode is magnesium, the cathodeis graphite. Under DC, the initial voltage is 10V, the cathode currentdensity is 200 mA, and electrolysis is carried out for 12 hours at 60°C. Remove the electrode after the electrolysis, we can get whitesuspension. Filter it under reduced pressure, wash the white solid withanhydrous ethanol, and we get magnesium ethylene glycol.

2. Preparation of Polyester, Including Esterification andPolycondensation:

Esterification Reaction:

Using terephthalic acid and ethylene glycol as raw materials, ethyleneglycol and terephthalic acid molar ratio of 2.0:1, addingpolyether-inhibitor calcium acetate, calcium acetate dosage ofterephthalic acid in an amount of 0.05% by weight. Start esterificationreaction under nitrogen atmosphere pressure, and control the pressure at0.3 MPa, the temperature at 260° C. When esterified water distillateamount reaches 92% of the theoretical value of the esterification,reaction ends.

Polycondensation Reaction:

Including polycondensation reaction of low vacuum phase andpolycondensation reaction high vacuum phase:

In the polycondensation reaction low-vacuum stage, add catalyst and thestabilizer trimethyl phosphate into the esterification product. Thedimethyl phosphate dosage is 0.02% of terephthalic acid by weight, andthe amount of catalyst is 0.02% of terephthalic acid by mass. Thepolycondensation reaction is started under the condition of negativepressure, the pressure is steadily pumped from the atmospheric pressureto the absolute pressure of 495 Pa, the temperature is controlled at265° C., and the reaction time is 40 minutes. The catalyst is a mixtureof magnesium ethylene glycol and antimony ethylene glycol, in whichmagnesium glycol and antimony ethylene glycol mass ratio is 3:1;

After the polycondensation reaction in the low-vacuum stage, the vacuumis continued to reduce the reaction pressure to 98 Pa, the reactiontemperature is controlled at 278° C., and the reaction time is 80minutes. The polyester sections are obtained by granulation.

3. Solvent Cleaning

Polyester sections are washed with water and rinsing agent ethyleneglycol monopropyl ether at 125° C. and 0.25 MPa for 4 hours. Afterwashing, the polyester sections are washed with hot water at 78° C. for12 minutes and then washed with cold water. After drying and cooling,the mass ratio of water to the rinsing agent is 100:4, the ratio of thepolyester section to the water and the rinsing agent, that is, the solidto liquid ratio is 1:9;

4. Solid-Phase Polycondensation:

The obtained polyester sections are solidified by polycondensation toincrease the intrinsic viscosity of the polyester sections to 1.1 dL/g,that is, high-viscosity sections.

5. The Main Process Parameters in Spinning:

The temperature of extrusion is 310° C.,

The air temperature of cooling is 30° C.,

The process of stretching, heat setting:

GR-1 speed 3600 m/min, temp: 80° C.,

GR-2 speed 4500 m/min, temp: 95° C.,

GR-3 speed 5600 m/min, temp: 255° C.,

GR-4 speed 5600 m/min, temp: 255° C.,

GR-5 speed 5650 m/min, temp: 255° C.,

GR-6 speed 5600 m/min, temp: 255° C.,

The winding speed is 5500 m/min.

The high-modulus low-shrinkage polyester industrial yarn obtained underthe conditions of a temperature of 177° C.×10 min×0.05 cN/dtex has thethy heat shrinkage rate of 2.05%. The high-modulus low-shrinkagepolyester industrial yarn according to the present invention has theaverage value of the crystal volume Vc of 232 nm³ and a fiber modulus of111 cN/dtex. Additionally, the linear density deviation rate is 1.4%,breaking strength is 7.1 cN/dtex, CV value of breaking strength is 2.4%,breaking extension is 13.2% and CV value of breaking extension is 6.9%.

EXAMPLE 3

A high-modulus low-shrinkage polyester industrial yarn preparationmethod, the main process is:

1. Preparation of Catalyst Magnesium Glycol:

Add ethylene glycol into the single-compartment electrolytic cell,magnesium chloride is electrolyte, the anode is magnesium, the cathodeis graphite. Under DC, the initial voltage is 8V, the cathode currentdensity is 160 mA, and electrolysis is carried out for 11 hours at 56°C. Remove the electrode after the electrolysis, we can get whitesuspension. Filter it under reduced pressure, wash the white solid withanhydrous ethanol, and we get magnesium ethylene glycol.

2. Preparation of Polyester, Including Esterification andPolycondensation:

Esterification Reaction:

Using terephthalic acid and ethylene glycol as raw materials, ethyleneglycol and terephthalic acid molar ratio of 1.8:1, addingpolyether-inhibitor sodium acetate, sodium acetate dosage ofterephthalic acid in an amount of 0.03% by weight. Start esterificationreaction under nitrogen atmosphere pressure, and control the pressure at0.2 MPa, the temperature at 255° C. When esterified water distillateamount reaches 95% of the theoretical value of the esterification,reaction ends.

Polycondensation Reaction:

Including poly condensation reaction of low vacuum phase andpolycondensation reaction high vacuum phase:

In the polycondensation reaction low-vacuum stage, add catalyst and thestabilizer trimethyl phosphite into the esterification product. Thetrimethyl phosphite dosage is 0.03% of terephthalic acid by weight, andthe amount of catalyst is 0.04% of terephthalic acid by mass. Thepolycondensation reaction is started under the condition of negativepressure, the pressure is steadily pumped from the atmospheric pressureto the absolute pressure of 495 Pa, the temperature is controlled at266° C., and the reaction time is 38 minutes. The catalyst is a mixtureof magnesium ethylene glycol and antimony ethylene glycol, in whichmagnesium glycol and antimony ethylene glycol mass ratio is 3:1;

After the polycondensation reaction in the low-vacuum stage, the vacuumis continued to reduce the reaction pressure to 99 Pa, the reactiontemperature is controlled at 277° C., and the reaction time is 70minutes. The polyester sections are obtained by granulation.

3. Solvent Cleaning

Polyester sections are washed with water and rinsing agent ethyleneglycol monobutyl ether at 128° C. and 0.25 MPa for 3 hours. Afterwashing, the polyester sections are washed with hot water at 75° C. for12 minutes and then washed with cold water. After drying and cooling,the mass ratio of water to the rinsing agent is 100:4, the ratio of thepolyester section to the water and the rinsing agent, that is, the solidto liquid ratio is 1:8;

4. Solid-Phase Polycondensation:

The obtained polyester sections are solidified by polycondensation toincrease the intrinsic viscosity of the polyester sections to 1.2 dL/g,that is, high-viscosity sections.

5. The Main Process Parameters in Spinning:

The temperature of extrusion is 295° C.

The air temperature of cooling is 25° C.,

The process of stretching, heat setting:

GR-1 speed 3200 m/min, temp: 78° C.,

GR-2 speed 3900 m/min, temp: 88° C.,

GR-3 speed 5700 m/min, temp: 252° C.,

GR-4 speed 5500 m/min, temp: 252° C.,

GR-5 speed 5640 m/min, temp: 252° C.,

GR-6 speed 5550 m/min, temp: 252° C.,

The winding speed is 5460 m/min.

The high-modulus low-shrinkage polyester industrial yarn obtained underthe conditions of a temperature of 177° C.×10 min×0.05 cN/dtex has thedry heat shrinkage rate of 1.98%. The high-modulus low-shrinkagepolyester industrial yarn according to the present invention has theaverage value of the crystal volume Vc larger than 230 mm³ and a fibermodulus of 114 cN/dtex. Additionally, the linear density deviation rateis 1.3%, breaking strength is 7.9 cN/dtex, CV value of breaking strengthis 1.5%, breaking extension is 11.1% and CV value of breaking extensionis 5.8%.

EXAMPLE 4

A high-modulus low-shrinkage polyester industrial yarn preparationmethod, the main process is:

1. Preparation of Catalyst Magnesium Glycol:

Add ethylene glycol into the single-compartment electrolytic cell,magnesium chloride is electrolyte, the anode is magnesium, the cathodeis graphite. Under DC, the initial voltage is 10V the cathode currentdensity is 150 mA, and electrolysis is carried out for 12 hours at 50°C. Remove the electrode after the electrolysis, we can get whitesuspension. Filter it under reduced pressure, wash the white solid withanhydrous ethanol, and we get magnesium ethylene glycol.

2. Preparation of Polyester, Including Esterification andPolycondensation:

Esterification Reaction:

Using terephthalic acid and ethylene glycol as raw materials, ethyleneglycol and terephthalic acid molar ratio of 1.2:1, addingpolyether-inhibitor sodium acetate, sodium acetate dosage ofterephthalic acid in an amount of 0.04% by weight. Start esterificationreaction under nitrogen atmosphere pressure, and control the pressure at0.2 MPa, the temperature at 258° C. When esterified water distillateamount reaches 96% of the theoretical value of the esterification,reaction ends.

Polycondensation Reaction:

Including polycondensation reaction of low vacuum phase andpolycondensation reaction high vacuum:

In the polycondensation reaction low-vacuum stage, add catalyst and thestabilizer acid triphenyl ester into the esterification product. Theacid triphenyl ester dosage is 0.03% of terephthalic acid by weight, andthe amount of catalyst is 0.04% of terephthalic acid by mass. Thepolycondensation reaction is started under the condition of negativepressure, the pressure is steadily pumped from the atmospheric pressureto the absolute pressure of 495 Pa, the temperature is controlled at265° C., and the reaction time is 30 minutes. The catalyst is a mixtureof magnesium ethylene glycol and antimony ethylene glycol, in whichmagnesium glycol and antimony ethylene glycol mass ratio is 3:1;

After the polycondensation reaction in the low-vacuum stage, the vacuumis continued to reduce the reaction pressure to 98 Pa, the reactiontemperature is controlled at 277° C., and the reaction time is 70minutes. The polyester sections are obtained by granulation.

3. Solvent Cleaning

Polyester sections are washed with water and rinsing agent ethyleneglycol monoethyl ether at 120° C. and 0.3 MPa for 5 hours. Afterwashing, the polyester sections are washed with hot water at 72° C. for12 minutes and then washed with cold water. After drying and cooling,the mass ratio of water to the rinsing agent is 100:4, the ratio of thepolyester section to the water and the rinsing agent, that is, the solidto liquid ratio is 1:8;

4. Solid-Phase Polycondensation:

The obtained polyester sections are solidified by polycondensation toincrease the intrinsic viscosity of the polyester sections to 1.2 dL/g,that is, high-viscosity sections.

5. The Main Process Parameters in Spinning:

The temperature of extrusion of 295° C.,

The air temperature of cooling is 25° C.,

The process of stretching, heat setting:

GR-1 speed 3500 m/min, temp: 78° C.,

GR-2 speed 4000 m/min, temp: 88° C.

GR-3 speed 5500 m/min, temp: 250° C.,

GR-4 speed 5600 m/min, temp: 250° C.,

GR-5 speed 5630 m/min, temp: 255° C.,

GR-6 speed 5500 m/min, temp: 255° C.,

The winding speed is 5500 m/min.

The high-modulus low-shrinkage polyester industrial yarn obtained underthe conditions of a temperature of 177° C.×10 min×0.05 cN/dtex has thedry heat shrinkage rate of 1.89%. The high-modulus low-shrinkagepolyester industrial yarn according to the present invention has theaverage value of the crystal volume Vc of 245 mm³ and a fiber modulus of116 cN/dtex. Additionally, the linear density deviation rate is 1.1%,breaking strength is 8.9 cN/dtex, CV value of breaking strength is 2.1%,breaking extension is 13.1% and CV value of breaking extension is 5.9%.

1. A high-modulus low-shrinkage polyester industrial yarn, wherein thehigh-modulus low-shrinkage polyester industrial yarn is obtained bysubjecting a polyester to dissolution, washing and solid statepolycondensation followed by spinning, the high-modulus low-shrinkagepolyester industrial yarn has a dry heat shrinkage rate of 2.0±0.25%under test conditions of 177° C.×10 min×0.05 cN/dtex, an average valueof the crystal volume Vc of the high-modulus low-shrinkage polyesterindustrial yarn is larger than 230 mm³, the high-modulus low-shrinkagepolyester industrial yarn has a fiber modulus of ≥100 cN/dtexm, thepolyester is obtained by esterification of terephthalic acid andethylene glycol and the polycondensation catalysed by a mixture ofmagnesium ethylene glycol and antimony ethylene glycol followed bygranulation; wherein a carboxyl end group is less than 15 mol/t, a masspercentage of oligomer is lower than 0.5%, and a weight percentage ofdiethylene glycol is lower than 0.5%; wherein the molecular formula ofmagnesium ethylene glycol is Mg(OCH₂CH₂OH)₂; wherein, during thedissolution and washing, the granulated sections are scoured and washedwith water and a rinsing agent at 120-130° C. and 0.2-0.3 MPa.
 2. Theyarn according to claim 1, wherein a linear density deviation of theyarn is ≤1.5%, a breaking strength of the yarn is ≥7.0 cN/dtex, the CVvalue of the breaking strength≤2.5%, a breaking extension of the yarn is20.0±1.5%, and the CV value of the breaking extension≤7.0%.
 3. The yarnaccording to claim 1, wherein a mass ratio of magnesium ethylene glycolto antimony ethylene glycol in their mixture is 2 to 3:1.
 4. A methodfor preparing the yarn, the method comprising: obtaining a polyester byesterification of terephthalic acid and ethylene glycol andpolycondensation catalyzed by a mixture of magnesium ethylene glycol andantimony ethylene glycol, a polyester section is obtained bygranulating, then performing dissolution, washing, and solid statepolycondensation on the polyester section; after measuring, extrusioncooling, oiling, stretching, heat setting and winding, the high-moduluslow-shrinkage polyester industrial yarn is prepared.
 5. The method forpreparing the yarn according to claim 4, the preparation method of thehigh-modulus low-shrinkage polyester industrial yarn includes:preparation of magnesium ethylene glycol adding ethylene glycol in asingle-compartment electrolytic cell, magnesium chloride is a supportingelectrolyte, an anode is comprised of magnesium, a cathode is graphite,operating the single-compartment electrolytic cell at 50 to 60° C. forabout 10 to 12 h under DC for an initial voltage 6 to 10V, wherein acathodic current density is 150 to 200 mA, after electrolysis a whitesuspension liquid is obtained followed by removing the electrodes,decompression filtration and washing by anhydrous alcohol, thenobtaining the magnesium ethylene glycol after drying; performing theesterification and polycondensation using terephthalic acid and ethyleneglycol as raw materials, adding polyether-inhibitor to obtainesterification products after reaction, the pressure of theesterification reaction is controlled in a range of atmospheric pressureto 0.3 MPa, the esterification reaction temperature is controlledbetween 250 to 260° C. finishing the esterification reaction when anamount of distillate water in the esterification reaction reaches 90% ofa theoretical value; performing a condensation reaction, including a lowvacuum stage and a high vacuum stage of the condensation reaction,wherein, in the low vacuum stage of the condensation reaction, adding acatalyst and a stabilizer into a product obtained from theesterification reaction; wherein the condensation reaction is performedunder a negative pressure, where the pressure is decreased graduallyfrom the atmospheric pressure to a pressure lower than the absolutepressure 500 Pa, and a temperature of the condensation reaction iscontrolled between 260 to 270° C., wherein the low vacuum stage of thecondensation reaction is carried out for 30 to 50 mins; wherein thecatalyst is the mixture of magnesium ethylene glycol and antimonyethylene glycol; in the high vacuum stage of the condensation reaction,continuously pumping vacuum after the low vacuum stage of thecondensation reaction to an absolute pressure lower than 100 Pa, the lowvacuum stage of the condensation reaction temperature is controlledbetween 275 to 280° C., and the low vacuum stage of the condensationreaction is carried out for 50 to 90 mins; then preparing the polyestersection through granulation; scouring and washing the polyester sectionwith water and a rinsing agent at 120 to 130° C. and 0.2 to 0.3 MPa for3 to 5 h followed by washing with water; performing solid statepolycondensation, wherein an intrinsic viscosity of the polyester israised to a value between 1.0 to 1.2 dL/g through the solid statepolycondensation, wherein a temperature of extrusion is 290 to 310° C.;wherein an air temperature of cooling is 20 to 30° C.; performingstretching and heat setting, wherein GR-1 at speed of 3000 to 3600m/min, temp: 75 to 80° C.; GR-2 at speed of 3800 to 4500 m/min, temp: 85to 95° C.; GR-3 at speed of 5000 to 5600 m/min, temp: 250 to 255° C.;GR-4 at speed of 5500 to 5600 m/min, temp: 250 to 255° C.; GR-5 at speedof 5630 to 5650 m/min, temp: 250 to 255° C.; GR-6 at speed of 5500 to5600 m/min, temp: 250 to 255° C.; wherein a winding speed is 5450 to5500 m/min.
 6. The process for preparing the yarn according to claim 5,wherein a molar ratio of the ethylene glycol to terephthalic acid is1.2:1 to 2.0:1.
 7. The process for preparing the yarn according to claim5, wherein a mass ratio of magnesium ethylene glycol to antimonyethylene glycol in mixture is 2 to 3:1; a mass of the catalyst is0.01-0.05% of the terephthalic acid; the stabilizer is selected from thegroup consisting of triphenyl phosphate, trimethyl phosphate andtrimethyl phosphite; the mass of the stabilizer is 0.01-0.05% of theterephthalic acid.
 8. The process for preparing the yarn according toclaim 5, wherein a mass ratio of water to the rinsing agent is 100:4 to100:3, and a ratio of polyester section to water and the rinsing agentis 1:5˜10, the rinsing agent is selected from the group consisting of2-ethoxyethanol, 2-propoxyethanol and ethylene glycol monobutyl ether.9. The process for preparing the yarn according to claim 5, wherein thecleaning is performed by washing the polyester sections with 60-80° C.water for 10-15 min after scouring the polyester sections, then washingwith cold water, and drying and cooling down the polyester sections. 10.The process for preparing the yarn according to claim 5, wherein thepolyether inhibitor is selected from the group consisting of sodiumacetate and calcium acetate, the mass of polyether-inhibitor is0.01-0.05% of terephthalic acid.